The invention concerns a method for the determination of several analytes in a multizone device as well as a device which is suitable therefor.
A recent development in medical diagnostics is to facilitate the diagnosis by the attending physician or by the patient himself of disease states by the detection of characteristic analytes in body fluids. When the clinical pictures are complex or when the cause of a disease cannot yet be exactly localized, it is often advisable or even necessary to carry out the determination of several different analytes. Thus for example in the case of tests for drug abuse individual tests for many drugs have to be carried out because of the multitude of possible drugs and the often unknown case history of the patient. Similar problems occur for example when diagnosing kidney and thyroid diseases or infectious diseases.
The so-called dry tests have proven to be reliable for the rapid and simple determination of analytes. In these a reagent or a multitude of reagents in dry form is located on a capillary carrier which is brought into contact with the sample liquid in order to carry out the test. The reagents dissolve in the liquid and give a characteristic signal for the analyte such as a change in colour, on the basis of which an analysis can be carried out. In simple tests it is sometimes possible to arrange the capillary carriers containing reagents on a single test element which is then immersed in the liquid in such a way that all carriers are wetted by the liquid. An example of such test elements is urea test strips which contain test zones for several analytes e.g. leucocytes, density, pH etc..
However, such a simple procedure of immersing the test zones once is for example not possible for immunological determinations of analytes such as antigens, haptens, and antibodies since these determinations are processes with a multistep reaction sequence. In this case the liquid containing the analyte passes along a test path containing several zones on which an exchange takes place of the various reagents between the liquid and the test zones. In one zone towards the end of the test path a characteristic signal for the presence of the analyte can be obtained and analysed.
In EP-A-0 467 175, to which U.S. Pat. No. 5,215,713 a method and a device are proposed for the determination of several analytes from a paste-like sample e.g. stool. The device contains an eluant application zone and several eluate transfer agents which ensure fluid contact with test strips for the desired determinations. Between the eluant application zone and the eluate transfer agents there is a region for the application of the paste-like sample. Between the eluant application zone and the sample application area there is a transport path for the pure eluant which is designed in such a way that the eluant flow is considerably retarded by the sample in order to achieve an effective elution of the relatively heterogeneous solid sample. Firstly the pure eluant is applied to this eluant application zone and is transported from there to the sample application area without change in the components. After elution of the analyte from the sample in the sample application area the eluate which now contains analyte flows through a transport zone which widens towards the test carriers wherein the transport paths are not separated from one another. The method described in EP-A-0 467 175 has the disadvantage that the various test strips and thus also the reagents come into contact with the eluate at different times and consequently in some cases different test results are obtained for the same test strips when using different eluate transfer agents. This can be particularly disadvantageous for a quantitative evaluation of analyses. Moreover the problems increase with an increasing number of eluate transfer agents.